Adding files for Ada

[Richard Kenner]

    Hopefully someone involved with moving libobjc etc. out to toplevel in 
    EGCS a few years ago can explain the issues and the advantages of having 
    libraries at toplevel; I don't remember them.

They would be very different for Ada because (1) the library is the
bulk of the files and (2) the compiler is partly in Ada, so it needs
the library to build.

    A single "make bootstrap" (or, better, a single "make") should suffice
    to build all of GCC - including Ada libraries and tools when they are
    included.

There's one additional line needed now (for the library build), but
somebody who's more familiar than I can presumable deal with this in
the Makefile that lives above the GCC directory.